Now you realize why many top coaches that utilize ketogenic diets to optimize body composition in their athletes require "carb up" days once per week to keep glycogen topped off for competition and maximal training.

Eating a ketogenic diet and relying on the occasional "carb up" day to keep glycogen stores topped up will inevitably mean training with depleted glycogen stores some of the time. If you train with depleted glycogen stores you will underperform and if you underperform often enough you will lose any adaptations to training you might have made. This is why athletes are advised to replenish their glycogen stores between workouts.